You do not have to upload a "full" spreadsheet every time you need to update your products. Sometimes, you might just need to update a few columns. In this example, let's say you just received a delivery and need to update your current inventory levels. in this example, we will use the OnHandQuantity column.
To update the available quantity for each product, you only need a spreadsheet with the ItemID column, the OnHandQuantity column in this case, and the IsDeleted column:
In doing so, you're telling our system which item(s) you're updating, which attribute(s)/parameters(s) you want to update for said item(s), and whether or not you want the item(s) to be visible, and available for ordering. Everything else will remain the same for the particular product(s) being updated.
This is a quick and easy way to focus on making specific changes, without having a large set of data in front of you, thus making it easier to quickly update your products.